U.S. patent application number 11/678640 was filed with the patent office on 2008-08-28 for unirradiated nuclear fuel component transport system.
Invention is credited to Brian E. HEMPY, John Dexter Malloy, Richard Forsythe Rochow.
Application Number | 20080203327 11/678640 |
Document ID | / |
Family ID | 39714830 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080203327 |
Kind Code |
A1 |
HEMPY; Brian E. ; et
al. |
August 28, 2008 |
UNIRRADIATED NUCLEAR FUEL COMPONENT TRANSPORT SYSTEM
Abstract
An unirradiated nuclear fuel assembly component transport system
that includes a clamshell-type inner liner that opens either along
its axial dimension or from the top to load and unload the fuel
assembly being transported. The exterior dimensions of the liner
conform to a generic overpack tubular container that protects the
liner from impact loads and fires.
Inventors: |
HEMPY; Brian E.; (Columbia,
SC) ; Malloy; John Dexter; (Goode, VA) ;
Rochow; Richard Forsythe; (Forest, VA) |
Correspondence
Address: |
WESTINGHOUSE ELECTRIC COMPANY, LLC
P.O. BOX 355
PITTSBURGH
PA
15230-0355
US
|
Family ID: |
39714830 |
Appl. No.: |
11/678640 |
Filed: |
February 26, 2007 |
Current U.S.
Class: |
250/506.1 |
Current CPC
Class: |
G21F 5/008 20130101 |
Class at
Publication: |
250/506.1 |
International
Class: |
G21F 5/00 20060101
G21F005/00 |
Claims
1. A shipping container system for a first nuclear fuel product
comprising: an elongated tubular container designed to receive and
support the first nuclear fuel product therein, an exterior of the
tubular container having at least two substantially flat walls,
with at least one circumferential end of at least one of the walls
having a hinged interface with a stationary wall of the container
to provide access to the interior thereof, the hinged wall
extending axially in the direction of one end of the container and
terminating a pre-selected distance short of the corresponding end
of the stationary wall, the stationary wall having a lateral groove
on an interior surface thereof extending in an orthogonal direction
to the axis of the container at an elevation starting substantially
at an elevation of the one end of the hinged wall, an access cover
slidable in the groove in the stationary wall to close off the one
end of the container so that the interior of the container may be
accessed either through the one end by sliding out the access cover
or from the side by rotating the hinged wall; an elongated, tubular
overpack having an axial dimension at least as long as the tubular
container, an internal cross-section larger than the tubular
container and an interior tubular channel having an axially
extending lower support section supporting a plurality of shock
mounts, with at least one of said plurality of shock mounts
positioned on either radial side of the lower support section, the
shock mounts support least one of the flat walls of the tubular
container in spaced relationship with the lower support section
when the overpack is supported in a horizontal position, with at
least one circumferential end of the lower support section having a
clamped interface substantially along the axial dimension thereof
to provide access to the interior of the overpack; and means for
supporting the overpack in the horizontal position.
2. The shipping container system of claim 1 including means for
locking the access cover in a closed position closing-off the one
end of the container.
3. The shipping container system of claim 2 wherein the means for
locking the access cover in a closed position is a pair of radially
extending arms that pivot proximate one end on each of the radially
extending arms that faces towards the center of the access cover,
the pivot enabling a distal end of the radially extending arms to
rotate from a position orthogonal to the axis of the elongated
tubular container towards the axis, each of the radially extending
arms extending at the distal end into a vertical slot in the
stationary wall that extends axially to the one end of the
stationary wall so that when the radially extending arm is rotated
into a horizontal position and engages the slot in the stationary
wall the access cover can not slide in the groove.
4. The shipping container system of claim 3 wherein the radially
extending arms are laterally restrained in a slot in an outwardly
projecting face of the access cover.
5. The shipping container system of claim 4 wherein the slot in the
outwardly projecting face of the access cover is formed from a
raised fork having two spaced prongs of a given width that form
walls of the slot in the outwardly projecting face of the access
cover.
6. The shipping container system of claim 5 wherein a hole is
formed in the width of the wall of each prong that is aligned with
a hole in the corresponding radially extending arm when the
radially extending arm is rotated in the horizontal position to
engage the slot in the stationary wall so that when a pin is
inserted through the holes when the radially extending arm is in
the horizontal position the radially extending arms are locked in
engagement with the slot in the stationary wall.
7. The shipping container system of claim 2 wherein the access
cover has an axially extending lip in the direction of the hinged
door that extends over an outer surface of the hinged door at the
one end when the access cover is fully seated in the groove so as
to prevent the hinged door from rotating toward an open
position.
8. The shipping container system of claim 1 having at least two
hinged walls that interface at their non-hinged circumferential
ends in a closed position with one of the non-hinged
circumferential ends having an axially extending tongue and the
other of the non-hinged circumferential ends having an axially
extending groove that mates with the tongue when the at least two
hinged walls are in the closed position.
9. The shipping container system of claim 1 wherein the stationary
and hinged walls of the elongated tubular container are constructed
from three extruded sections.
10. The shipping container system of claim 1 wherein the access
cover includes a hold down plate supported on an underside of the
access cover, the hold down plate being adjustable in the axial
direction to bring pressure on the first nuclear product to secure
the first nuclear product against a bottom member of the elongated
tubular container.
11. The shipping container system of claim 10 including a recess in
the underside of the access cover in which the hold down plate can
be withdrawn.
12. The shipping container system of claim 10 wherein an axial
elevation of the hold down plate is adjusted from a top of the
access cover.
13. The shipping container system of claim 1 wherein the access
cover has a thickness substantially equal to the width of the
groove in the stationary wall.
14. The shipping container system of claim 1 wherein the first
nuclear fuel product comprises a fuel assembly having a hexagonal
cross-section and the stationary walls and hinged walls of the
tubular member are configured in a hexagon when in a closed
position to closely match the contour of the fuel assembly.
15. The shipping container system of claim 1 wherein the hinged
wall interface with the stationary wall is coupled by a single
hinge pin.
16. An elongated tubular shipping container designed to receive and
support a first nuclear fuel product therein, comprising: an
exterior of the tubular container having at least two substantially
flat walls, with at least one circumferential end of at least one
of the walls having a hinged interface with a stationary wall of
the container to provide access to the interior thereof, the hinged
wall extending axially in the direction of one end of the container
and terminating a pre-selected distance short of the corresponding
end of the stationary wall, the stationary wall having a lateral
groove on an interior surface thereof at an elevation starting
substantially at an elevation of the one end of the hinged wall; an
access cover slidable in the groove in the stationary wall to close
off the one end of the container; and wherein the interior of the
container may be accessed either through the one end by sliding out
the access cover or from the side by rotating the hinged wall.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a shipping container for nuclear
fuel components and, in particular, to such a container for
unirradiated nuclear fuel assemblies and nuclear fuel rods.
[0003] 2. Related Art
[0004] In the shipping and storage of unirradiated nuclear fuel
elements and assemblies which contain large quantities and/or
enrichments of fissile material, U.sup.235, it is necessary to
assure that criticality is avoided during normal use, as well as
under potential accident conditions. For example, nuclear reactor
fuel shipping containers are licensed by the Nuclear Regulatory
Commission (NRC) to ship specific maximum fuel enrichments; i.e.,
weights and weight-percent U.sup.235, for each fuel assembly
design. In order for a new shipping container design to receive
licensing approval, it must be demonstrated to the satisfaction of
the NRC that the new container design will meet the requirements of
the NRC rules and regulations, including those defined in 10 CFR
71. These requirements define the maximum credible accident (MCA)
that the shipping container and its internal support structures
must endure in order to maintain the sub-criticality of the fuel
assembly housed therein.
[0005] U.S. Pat. No. 4,780,268, which is assigned to the assignee
of the present invention, discloses a shipping container for
transporting two conventional nuclear fuel assemblies having a
square top nozzle, a square array of fuel rods and a square bottom
nozzle. The container includes a support frame having a vertically
extending section between the two fuel assemblies which sit side by
side. Each fuel assembly is clamped to the support frame by
clamping frames which each have two pressure pads. This entire
assembly is connected to the container by a shock mounting frame
and a plurality of shock mountings. Sealed within the vertical
section are at least two neutron absorber elements. A layer of
rubber cork cushioning material separates the support frame and the
vertical section from the fuel assemblies.
[0006] The top nozzle of each of the conventional fuel assemblies
is held along the longitudinal axis thereof by jack posts with
pressure pads that are tightened down to the square top nozzle at
four places. The bottom nozzle of some of these conventional fuel
assemblies has a chamfered end. These fuel assemblies are held
along the longitudinal access thereof by a bottom nozzle spacer
which holds the chamfered end of the bottom nozzle.
[0007] These, and other shipping containers, e.g., RCC-4, for
generally square cross-sectional geometry pressurized water reactor
(PWR) fuel assemblies used by the assignee of the present
invention, are described in Certificate of Compliance Number 5454,
Docket Number 71-5450, U.S. Nuclear Regulatory Commission, Division
of Fuel Cycle and Material Safety, Office of the Nuclear Material
Safety and Safeguards, Washington, D.C. 20555.
[0008] U.S. Pat. No. 5,490,186, assigned to the assignee of the
present invention, describes a completely different nuclear fuel
shipping container designed for hexagonal fuel, and more
particularly, for a fuel assembly design for a Soviet-style VVER
reactor. Still, other shipping container configurations are
required for boiling water reactor fuel.
[0009] There is a need, therefore, for an improved shipping
container for a nuclear fuel assembly that can be employed
interchangeably with a number of nuclear reactor fuel assembly
designs.
[0010] There is a further need for such a fuel assembly shipping
container that can accommodate a single assembly in a lightweight,
durable and licensable design.
[0011] These and other needs have been partially resolved by U.S.
Pat. No. 6,683,931, issued Jan. 27, 2004 and assigned to the
assignee of the instant invention. The shipping container described
in this latter patent includes an elongated inner tubular liner
having an axial dimension at least as long as a fuel assembly. The
liner is preferably split in half along its axial dimension so that
it can be separated like a clamshell for placement of the two
halves of the liner around the fuel assembly. The external
circumference of the liner is designed to be closely received
within the interior of an overpack formed from an elongated tubular
container having an axial dimension at least as long as the liner.
Preferably, the walls of the tubular container are constructed from
relatively thin shells of stainless steel and the liner is
coaxially positioned within the tubular container with close-cell
polyurethane disposed in between. Desirably, the inner shell
includes boron impregnated stainless steel. The tubular liner
enclosing the fuel assembly is slidably mounted within the overpack
and the overpack is sealed at each end with end caps. The overpack
preferably includes circumferential ribs that extend around the
circumference of the tubular container at spaced axial locations
that enhance the circumferential rigidity of the overpack and form
an attachment point for peripheral shock-absorbing members. An
elongated frame, preferably of a birdcage design, is sized to
receive the overpack within the external frame in spaced
relationship with the frame. The frame is formed from axially
spaced circumferential straps that are connected to
circumferentially-spaced, axially-oriented support ribs that
fixedly connect the straps to form the frame design. A plurality of
shock absorbers are connected between certain of the straps and at
least two of the circumferential ribs extending around the
overpack, to isolate the tubular container from a substantial
amount of any impact energy experienced by the frame, should the
frame be impacted.
[0012] Although the shipping container described in the
aforementioned '931 patent is a substantial improvement in that it
can accommodate different fuel assembly designs through the use of
complementary liners while employing the same overpack and birdcage
frame, that improvement has been taken one step further by U.S.
Pat. No. 6,748,042, assigned to the assignee of the instant
invention. The '042 patent describes a transport system that
provides a liner and overpack system that will achieve the same
objectives as the '931 patent while further improving the
protective characteristics of the transport system and the ease of
loading and unloading the nuclear fuel components transported
therein. The shipping container includes an elongated tubular
container, shell or liner designed to receive and support a nuclear
fuel product such as a fuel assembly therein. The interior of the
tubular liner preferably conforms to the external envelope of the
fuel assembly. The exterior of the tubular container has at least
two substantially abutting flat walls which extend axially. In the
preferred embodiment, the cross-section of the tubular member is
rectangular or hexagonal to match the outer envelope of the fuel
assembly and three of the corner seams are hinged so that removal
of all the kingpins along a seam will enable two of the sidewalls
to swing open and provide access to the interior of the tubular
container. The tubular container or liner is designed to seat
within an overpack for transport. The overpack is a tubular package
having an axial dimension and cross-section larger than the tubular
liner. The overpack is split into a plurality of circumferential
sections (for example, two sections, a lower support section and an
upper cover, or three sections, a lower support section and two
upper cover sections) that are respectively hinged to either
circumferential side of the lower support section and joined
together when the overpack is closed. The lower support section
includes an internal central V-shaped groove that extends
substantially over the axial length of the overpack a distance at
least equal to the axial length of the tubular liner. Shock mounts
extend from both radial walls of the V-shaped groove to an
elevation that will support the tubular liner in spaced
relationship to the groove. The axial location, number, size and
type of shock mount employed is changeable to accommodate different
loadings. The tubular liner is seated on the shock mounts,
preferably with a corner of the liner aligned above the bottom of
the V-shaped groove. The top cover section (sections) of the
overpack has a complementary inverted V-shaped channel that is
sized to accommodate the remainder of the tubular liner with some
nominal clearance approximately equal to the spacing between the
lower corner of the tubular liner and the bottom of the V-shaped
groove. The ends of the overpack are capped and the overpack
sections are latched.
[0013] Though the transport system of the '402 patent provides a
substantial improvement in the protective characteristics and ease
of loading and unloading of the nuclear fuel components being
transported, further improvement in the ease of loading and
unloading the liner is desired.
SUMMARY OF THE INVENTION
[0014] This invention provides an improved liner that facilitates
the loading and unloading of nuclear components, especially
components having hexagonal contour such as the VVER nuclear fuel
assemblies. The liner comprises an elongated tubular container
designed to receive and support the nuclear fuel product or
components therein. An exterior of the tubular container has at
least two substantially flat walls with at least one
circumferential end of at least one of the walls having a hinged
interface with a stationary wall of the container to provide access
to the interior thereof. The hinged wall extends axially in the
direction of one end of the container and terminates a pre-selected
distance short of the corresponding end of the stationary wall. The
stationary wall has a lateral groove on an interior surface thereof
at an elevations starting substantially at the elevation of the one
end of the hinged wall. An access cover is slidable in the groove
in the stationary wall to close off the one end of the container so
that the interior of the container may be accessed either through
the one end by sliding out the access cover, or from the side by
rotating the hinged wall. The elongated tubular container has the
other end opposite the one end capped and sealed and is sized to
fit within the overpack of the '042 patent.
[0015] Preferably, a mechanism is provided for locking the access
cover in a closed position when the container is prepared for
transport. Desirably, the locking mechanism is a pair of radially
extending arms that pivot proximate one end on each of the radially
extending arms that faces towards the center of the access cover.
The pivot enables the radially extending arms to rotate from a
position orthogonal to the axis of the elongated tubular container
toward the axis. Each of the radially extending arms extends at a
distal end into a slot in the stationary wall that extends axially
to the one end of the stationary wall so that when the radially
extending arms are rotated into a horizontal position and engage
the slot in the stationary wall, the access cover cannot slide in
the groove. In this preferred embodiment, the radially extending
arms are laterally restrained in a slot in an outwardly projecting
face of the access cover. Preferably, the outwardly-projecting face
of the access cover is formed from a raised fork having two spaced
prongs of a given width that form the walls of the slot in the
outwardly-projecting face of the access cover. A hole is formed in
the width of the wall of each prong that is aligned with a hole in
the corresponding radially extending arm when the radially
extending arm is rotated in the horizontal position to engage the
slot in the outwardly-projecting face of the access cover. Thus,
when a pin is inserted through the holes when the radially
extending arm is in the horizontal position, the radially extending
arm is locked in engagement with the slot in the stationary
wall.
[0016] Preferably, the liner has at least two hinged walls that
interface at their non-hinged circumferential ends in a closed
position. One of the non-hinged circumferential ends of the hinged
wall has an axially extending tongue and the other of the
non-hinged circumferential ends of the hinged wall has an axially
extending groove that mates with the tongue when the two hinged
walls are in the closed position. Preferably, the stationary and
hinged walls of the liner are constructed from three extruded
sections.
[0017] In another embodiment, the access cover has an
axially-extending lip extending in the direction of the hinged
door. The lip of the access cover extends over an outer surface of
the hinged door at the one end when the access cover is fully
seated in the groove. Thus, when the access cover is fully seated
to close off the one end of the tubular liner, it prevents the
hinged door from rotating toward an open position.
[0018] In still another embodiment, the access cover includes a
hold-down plate supported on an underside of the cover. The
hold-down plate is adjustable in the axial direction to bring
pressure on the nuclear product being transport to secure the
nuclear product against a bottom member of the elongated tubular
liner. Preferably, in the withdrawn position, the hold-down plate
is secured within a recess in the access cover.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] A further understanding of the invention can be gained from
the following description of the preferred embodiments when read in
conjunction with the accompanying drawings in which:
[0020] FIG. 1 is a side view of a nuclear fuel assembly having a
top nozzle, a hexagonal array of fuel rods, and a bottom
nozzle;
[0021] FIG. 2 is a front view of the shipping container system of
this invention, showing neutron moderated material lining the inner
channel of the overpack;
[0022] FIG. 3 is a front view of the shipping container system of
this invention with thermal insulation lining the interior of the
stainless steel shell and neutron-absorbing material lining the
exterior of the tubular container surrounding a fuel assembly;
[0023] FIG. 4 is a perspective view of the latch mechanism used to
anchor the overpack segments together;
[0024] FIG. 5 is a perspective view of the tubular container
housing a nuclear fuel assembly with two sides of the tubular
container swung open;
[0025] FIG. 6 is a top view of the tubular container having two
hinged walls with all six sidewalls closed;
[0026] FIG. 7 is a perspective view of the top end of the tubular
liner of this invention showing the access cover removed;
[0027] FIG. 8 is a perspective view showing the underside of the
access cover to the tubular liner; and
[0028] FIG. 9 is a perspective view of the top end of the tubular
liner of this invention showing the access cover seated in a closed
position with the locking mechanism shown open.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] In the preferred embodiment, this invention provides a
transport system for transporting nuclear fuel assemblies and
particularly, nuclear fuel assemblies having a hexagonal profile
such as those employed in the VVER nuclear reactors. An exemplary
VVER 1000 nuclear fuel assembly 2 manufactured by Westinghouse
Electric Company LLC, which is the assignee of the present
invention, is shown in FIG. 1. The fuel assembly 2 includes a top
nozzle 4, a hexagonal array of a plurality of fuel rods 6 and a
bottom nozzle 8. The top nozzle 4, the fuel rods 6 and the bottom
nozzle 8 are positioned about a central longitudinal axis 9 of the
fuel assembly 2. The top nozzle 4 includes a cylindrical outer
barrel 10 having a top end 11 and two lifting lugs 13 (only one is
shown), a cylindrical inner barrel 12 which telescopes into the
outer barrel 10, and a shoulder 14 between the outer barrel 10 and
the inner barrel 12. The fuel rods 6 are held in the hexagonal
array by a plurality of hexagonal grids 16 spaced longitudinally
along the fuel rods 6. The exemplary fuel assembly 2 includes 9
hexagonal grids 16. Each of the grids 16 has six sides.
[0030] The bottom nozzle 8 includes a longitudinally-extending
recess 18 formed by a hexagonal barrel 20, a spherical taper 22,
and a cylindrical barrel 24 which has a diameter smaller than the
hexagonal barrel 20. Disposed on the cylindrical barrel 24 are two
alignment pins 25 (only one is shown). The spherical taper 22
interconnects the hexagonal barrel 20 and the cylindrical barrel 24
which forms a bottom end 26 of the fuel assembly 2. The
longitudinally-extending recess 18 tapers towards the bottom end 26
and also forms an internal shoulder between the hexagonal barrel 20
and the bottom end 26. The fuel assembly 2 will be secured within a
liner 28 which will be described hereafter with respect to FIGS. 3,
5, 6, 7, 8 and 9. The liner 28 will, in turn, be secured within an
overpack 30 which is intended to protect the fuel assembly 2 from
impacts and fires. The overpack 30 and the internal components of
the nuclear fuel product containment and transport system of this
invention is illustrated in FIG. 2. A tubular liner, sometimes
referred to as container or shell 28, constructed from a material
such as aluminum, houses the nuclear fuel assembly 2. The tubular
liner 28 is suspended over a V-shaped groove 32 in the overpack 30
and supported on shock mounts 32 that are affixed in a recess 34 in
an upper wall section of the groove 32 and spaced along the axial
length of the lower overpack support section 36. The shock mounts
can be those identified by part number J-3424-21, which can be
purchased from Lord Corporation, having offices in Cambridge
Springs, Pa. Angle irons 24 can be used at the corners of the
tubular liner 28 to spread the load on the liner walls. The number
and resiliency of the shock mounts are chosen to match the weight
of the liner, which depends upon the nuclear product being
transported within the liner 28. The orientation of the lower
section 36 of the overpack 30 is fixed by the legs 40 so that the
weight of the liner 28 holds the liner centered in the groove 32.
One capped end 42 of the overpack 30 forms part of the lower
overpack support section 36, while a second capped end 44 is formed
as an integral part of the top cover 46. The end 44 of the upper
overpack segment 46 seals against the lip 48 in the lower support
section 36. Keys 50 on each side of the upper section 46 of the
overpack 30 fit in complementary keyways in the lower overpack
support section 36, as can be better appreciated from the frontal
view shown in FIG. 3.
[0031] FIG. 3 shows a frontal view of the shipping container system
27 of this invention with the end plate 44 removed. Both the top
segment 46 and the bottom segment 36 of the overpack 30 are formed
from hollow stainless steel sheet 52. For example, an 11 gauge
stainless steel shell filled with polyurethane can be employed.
Preferably, in this embodiment, the polyurethane has a minimum 3''
(7.62 cm) thickness. In the preferred embodiment, the hollow
channel in the overpack 54 is shaped to substantially conform to
the outer profile of the tubular liner 28 and the walls of the
hollow channel 54 can be lined with a neutron-absorbing material,
such as a half-inch (1.27 cm) of borosilicate. Alternately, the
outer surface of the tubular liner 28 can be lined with a
neutron-absorbable material, such as a 1/8'' (0.318 cm) thick layer
of borosilicate, or a combination of neutron-absorbing material on
the walls of the tubular liner 28 and the walls of the hollow
channel 54 can be employed. FIG. 3 provides a better view of the
recess 34 that the shock mounts 32 are mounted in than can be
derived from FIG. 2. Similarly, the keys 50 and keyways 56 that aid
in positioning the top section 46 on the lower support section 36
of the overpack 30 are shown more clearly in FIG. 3. The top and
bottom overpack sections 46 and 36, respectively, are formed from a
stainless steel shell 58 that is filled with polyurethane 60.
Thermal insulation 62 can be incorporated to line the interior of
the stainless steel sheet overpack shell 52.
[0032] The top segment 46 of the overpack is latched to the bottom
support segment 36 in the preferred embodiment using the latch
assembly shown in FIG. 4. Both the lip 53 on the upper overpack
section 46 and the lip 55 on the lower overpack section 36 include
a plurality of axially-spaced slots. A latchbar 66 is affixed to
either the upper lip 53 or the lower lip 55 in a manner to permit
the clamp arm 64 to slide within a corresponding slot in the lip.
For example, with the latchbar 66 coupled to the lower lip 55, the
clamp arm 64 would protrude through the corresponding slot in a
downward direction and have a large protruding end to anchor the
latchbar 66 to the lower lip 55. The upper clamp arm 64 can have an
L-shape, as shown in FIG. 4, so that when the lip 53 is seated over
its corresponding clamp arm 64, the latchbar 66 can be moved in a
direction into the Figure to lock the upper section 46 to the lower
section 36 of the overpack 30. The clamp arm 64 can then be secured
in that locked position and an external lever can be used to slide
the latchbar 66 to an open and closed position with an approximate
4'' stroke desirable. To facilitate the locking and unlocking
action, a low-friction coating can be applied to the sliding
surfaces.
[0033] FIG. 5 illustrates a perspective view of an open tubular
liner 28 with a fuel assembly 2 positioned therein. As previously
mentioned with respect to FIG. 1, the fuel assembly 2 is made up of
a parallel spaced array of fuel elements 6 that are maintained in
spaced relationship and in position by grid straps 16, bottom
nozzle 8 and a top nozzle which is not shown. The grid straps are
constructed in an egg crate design to maintain the spacing between
the fuel elements 6 that form flow channels for the reactor coolant
to flow through during reactor operation. The fuel assembly 2 is
seated on a neoprene or cork rubber bottom pad 72 which is affixed
to the bottom 68 of the tubular liner 28. The neoprene or cork
rubber pad 72 supports and cushions the fuel assembly 2. A similar
arrangement is provided above the fuel assembly 2 by a neoprene or
cork rubber hold down plate that is supported by a top access cover
to the tubular liner 28 as will be more fully described with regard
to FIG. 8. In this embodiment, the tubular container has four
stationary sides, 74, 76, 78 and 80 (shown in FIG. 6) which are
affixed to the bottom 68 of the tubular liner 28. The tubular liner
28 has two movable sides 70 and 71 which are hinged to the adjacent
edges of the stationary sides 74 and 78 through hinges 82 that
rotate around a kingpin 84. The two movable sides are in turn
connected, when latched, by similar hinges 82, with the insertion
of the kingpin in the hinge forming the latch. In this way, the
movable sides 70 and 71 can be opened from any of the hinged seams
to provide access to the interior of the tubular liner 26 from a
number of different directions to facilitate loading and unloading
in different environments that may present obstructions. For quick
access, the hinges connecting a given side may be connected by a
single kingpin that extends through the lower hinge and up through
each of the individual hinges 82 extending up the hinged seam. The
tubular liner 28 is preferably constructed out of aluminum of a
thickness, for example, of 0.375'' (0.9525 cm).
[0034] The interior walls of the sides 70, 71, 74, 76, 78 and 80
are covered with an iron ferrite composite sheet 86 and neoprene or
cork rubber pads with magnetic backing 88 attached and affixed by
the magnetic force at the grid elevations to seat the neoprene or
cork rubber side of the pads against the outside straps of the
grids 16. The magnetic coupling on the pads make them adjustable to
accommodate different nuclear fuel component designs. The neoprene
or cork rubber pads are not as hard as the material that the grids
are constructed of and secures the grids in position when the
movable sides 70 and 71 are in the closed position, without
damaging the grids, and cushions the fuel assembly 2 during
transport. The inside of the tubular liner 28 can be used to
transport other fuel components, such as fuel rods, separately by
employing inserts within the tubular container 28 that will hold
those components securely. Alternatively, clips on the backs of the
neoprene or cork rubber pads can be supported in slots at multiple
elevations on the interior walls of the sides 70, 71, 74, 76, 78
and 80. Axial adjustment of the pads can be made by moving the pads
from slot to slot. FIG. 6 provides a better view of the iron
ferrite composite sheet 86 and hinged locations. FIG. 6 shows the
bottom 68 of the tubular line 28 supported on the shock mounts 32
within the overpack 30. From FIG. 6, it can be appreciated that one
of the opening edges of the movable walls 70 and 71 has a groove
that extends axially down its entire length while the other of the
edges of the movable walls 70 and 71 has an axially extending
tongue that mates with the groove when the movable walls 70 and 71
are in the closed position, as shown in FIG. 6. Though the
preferred embodiment is shown with a hexagonal liner compatible
with VVER 1000 fuel, it should be appreciated that the novel
features of this invention can be applied equally as well to a
square reactor fuel assembly such as those employed in Westinghouse
Electric Company LLC designed reactors. This invention has
particular benefit for handling hexagonal fuel because it provides
additional choices for access to the interior of the liner for
loading the hexagonal fuel which can present handling difficulties
that are not encountered with square fuel configurations.
[0035] FIG. 7 shows the top 90 of the liner 28 with an access cover
92 in the open position. With the access cover 92 removed from the
top of the tubular liner 28, as shown in FIG. 7, the fuel assembly
2 may be loaded into the liner from the top of the liner as an
alternative to being loaded from the side through the movable sides
70 and 71. To close the liner 28, the access cover 92 slides within
a circumferential groove 94 in the stationary walls 74, 76, 78 and
80. The access cover 92, on its upper surface 103, has
diametrically opposed raised forks 104 that are connected by a
central hub 112. The tines 114 of the forks 104 define a groove 113
within which radially extending arms 98 are laterally restrained
and pivot about pivot points 96. When the access cover 92 is in the
closed position seated within the grooves 94, the radially
extending arms 98 can be rotated about the pivots 96 to the
horizontal position in which they engage the slots 108 in the upper
end 90 of the stationary walls 74 and 80, thus locking the access
cover 92 in the closed position. A retaining pin or lock can then
be inserted through aligned holes 100 in the fork tines and 102 in
the radially extending arms 98 to restrain the radially extending
arms in the locked position. A downwardly projecting lip 110 on the
access cover 92 seats up against the outer upper surface of the
movable sides 70 and 71 to lock the movable sides in the closed
position when the access cover 92 is in place fully seated in the
groove 94.
[0036] FIG. 8 shows another perspective view of the upper portion
of the liner 28 with the access cover 92 in an open position
showing the underside of the access cover. The underside of the
access cover has a recess 116 in which the hold down plate 118 can
be withdrawn as the access cover 92 is inserted into the annular
groove 94 to close off the top of the tubular liner 28. A hole in
the top of the access cover 106 (shown in FIG. 7) provides access
to an adjustment screw that adjust the axial elevation of the hold
down plate 118 so that it brings pressure against the top nozzle 4
of the fuel assembly 2 to restrain the fuel assembly in a secure
position within the tubular liner 28.
[0037] FIG. 9 shows the access cover 92 in the fully seated closed
position locking the movable sides 70 and 71 in the closed
position.
[0038] While specific embodiments of the invention have been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to those details
could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular embodiments disclosed are
meant to be illustrative only and not limiting as to the scope of
the invention which is to be given the full breadth of the appended
claims and any and all equivalents thereof.
* * * * *